Remote copy system

ABSTRACT

In asynchronous remote copy, there is time difference between data update and remote copy in a primary storage system. The primary storage system loses data unreflected on a secondary storage system in disaster and cannot control the amount of data lost. The primary storage system obtains the data reflection state of remote copy between it and the secondary storage system to manage the amount of data update delay between the storage systems. When the amount of delay meets a configured start condition, a process of reducing the amount of delay is started. When the amount of delay meets a separately configured stop condition, the process of reducing the amount of delay is stopped. The configuration of whether the process of reducing the amount of delay is performed and the configuration of the conditions are performed from outside.

The present application is a continuation of application Ser. No.10/843,379, filed May 12, 2004, now U.S. Pat. No. 7,143,253, whichclaims priority from Japanese application No. 2004-070128, filed on Mar.12, 2004, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a remote copy technique duplicatingdata stored in a storage system to another storage system.

As a technique preventing data loss in a storage system due to disaster,there is a technique duplicating data to a storage system at a remotesite (remote copy). Here, the storage system includes a storage devicesuch as a disk and a storage controller coupled to the storage devicefor controlling input and output of data to/from the storage device. Theremote copy is a technique in which a storage system at a primary site(hereinafter, also called a primary storage system) transfers data inthe source storage system to another storage system (hereinafter, alsocalled a secondary storage system) at a remote site (hereinafter, alsocalled a secondary site), and the target storage system stores the datareceived from the source storage system in a storage device in thetarget storage system. As for the remote copy, disclosed is a techniqueduplicating data not via a host computer (hereinafter, called a host)between different storage controllers (see Patent Document 1).

Here, Patent Document 1 refers to U.S. Pat. No. 6,408,370.

SUMMARY OF THE INVENTION

In the above prior art, the primary storage system transfers write datato the secondary storage system asynchronous to a write request from thehost computer. The primary storage system in disaster loses datauntransferred to the secondary storage system. The difference in theamount of written data (the amount of update data) or the difference(deviation) in write timing between the primary storage system and thesecondary storage system is called the amount of delay of asynchronousremote copy. When the amount of delay is larger, the amount of data ofthe primary storage system lost in disaster is increased. Whenattempting to reduce the amount of delay, the system configuration islarger and the performance to the host computer is decreased. In theasynchronous remote copy, the amount of delay of the asynchronous remotecopy must be controlled according to the request level of the user.

To solve the above problems, a computer system has: a primary sitehaving a host computer and a first storage system coupled to the hostcomputer; and a secondary site having a second storage system, whereinthe first storage system is coupled to the second storage system via acommunication line, wherein the first storage system, when receiving awrite request from the host computer, transfers write data transferredaccording to the write request to the second storage system via thecommunication line. The second storage system writes the write datatransferred from the first storage system into a second storage areaowned by the second storage system. The first storage system obtains,from the second storage system, information indicating that the secondstorage system has written the write data into the second storage areato have the amount of delay of data write between the first storagesystem and the second storage system.

The amount of delay may be any one of time difference in data write, thedifference in the number of data writes, and the difference in theamount of data of data write between the first storage system and thesecond storage system.

A process of reducing the amount of delay is operated when the amount ofdelay exceeds a predetermined threshold value.

The operation reducing the amount of delay may be any one of anoperation delaying a write completion report of remote copy, anoperation increasing the priority of asynchronous remote copy, and anoperation increasing the number of paths of asynchronous remote copy.

The amount of delay may be managed by the host computer.

Consequently, the amount of delay of asynchronous remote copy betweenthe primary storage system and the secondary storage system can bereduced as necessary, and the amount of data of the primary storagesystem lost in disaster can be within a configuration value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a hardware configuration example of acomputer system according to a first embodiment of the presentinvention;

FIG. 2 is a diagram showing an example of the logic configuration of thecomputer system according to the first embodiment;

FIG. 3 is a diagram showing an example of volume management information;

FIG. 4 is a diagram showing an example of consistency group managementinformation;

FIG. 5 is a diagram showing an example of asynchronous remote copy writedata information;

FIG. 6 is a diagram showing an example of configuration information oncontrol of the amount of delay of asynchronous remote copy;

FIG. 7 is a diagram showing an example of a pair create process ofasynchronous remote copy;

FIG. 8 is a diagram showing an example of the operation of a process ofcontrolling the amount of delay of asynchronous remote copy according tothe first embodiment;

FIG. 9 is a diagram showing an example of a process of updating theamount of delay of asynchronous remote copy at write request;

FIG. 10 is a diagram showing an example of a process of updating theamount of delay of asynchronous remote copy;

FIG. 11 is a diagram showing an example of a start decision process of aprocess of reducing the amount of delay;

FIG. 12 is a diagram showing an example of a stop decision process of aprocess of reducing the amount of delay during the process of reducingthe amount of delay; and

FIG. 13 is a diagram showing an example of a process of controlling theamount of delay of asynchronous remote copy according to a secondembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

Embodiments of the present invention will be described below using FIGS.1 to 13.

A first embodiment of the present invention will be described usingFIGS. 1 to 12.

(I) The Configuration of a Computer System

The configuration of a computer system according to the first embodimentof the present invention will be described using FIG. 1.

FIG. 1 is a diagram showing the hardware configuration of the computersystem according to the first embodiment of the present invention.

FIG. 2 is a diagram showing the functional configuration of the computersystem according to the first embodiment of the present invention.

In the computer system of this embodiment, sites conjunctly performprocesses and each of the sites has a host computer and s storagesystem.

Here, a first site is called a “primary site”, a second site is called a“secondary site”, and an example performing remote copy from the primarysite to the secondary site will be described. A host computer belongingto the primary site is called a “primary host computer”, and a storagedevice belonging to the primary site is called a “primary storagesystem”. The secondary site is alike.

As shown in FIG. 1, a primary site 100A has a primary host computer 110Aand a primary storage system 120A, a secondary site 100B has a secondaryhost computer 110B and a secondary storage system 120B, and a managementterminal 130 is coupled to them.

The primary site 100A and the secondary site 100B may have a pluralityof primary host computers 110A and a plurality of secondary hostcomputers 110B, respectively.

Each of the host computers 110 (the primary host computer 110A and thesecondary host computer 110B) is a computer having a processor 111, amain memory 112, and an input/output processing unit 113. Specifically,it is a work station, microcomputer, or a mainframe computer.

Each of the storage systems 120 has a storage controller 140, one ormore storage devices 121, and a maintenance terminal 122. The storagedevice 121 is an auxiliary storage device such as a magnetic diskstorage device or an optical disk storage device. The storage system 120may not have the maintenance terminal 122. The storage controller 140has a host computer input/output processing unit 141, a cache memory142, a disk input/output processing unit 143, a processor 144, and acontrol memory 145.

The host computer is coupled to the storage system via a hostcomputer-storage system network 150 such as a LAN (Local Area Network)or SAN (Storage Area Network). The processor 111 and the main memory 112of each of the host computers are coupled to the host computerinput/output processing unit 141 of the storage system 120 via theinput/output processing unit 113 and the host computer-storage systemnetwork 150.

The storage systems are coupled via a storage system network 160. Ingeneral, the storage system network 160 is often a global network suchas a public line and is often rented for pay from a communicationservice provider. For the safety of the system, in order to keep awayfrom each other (in order that both sites cannot suffer failure at thesame time), the global network is often used. When the storage systemsare in the same room, in the same building, or in buildings adjacent toeach other, a local network may be used. Such network form does notlimit the present invention.

The management terminal 130 is also a computer having a processor and amain memory. The management terminal 130, the primary host computer110A, the secondary host computer 110B, the primary storage system 120A,and the secondary storage system 120B are mutually coupled via a network170 such as a LAN or WAN.

The functional configuration of such computer system is as shown in FIG.2.

In each of the storage controllers 140, a copy management program 221 asa program controlling data transfer between the storage systems 120, anasynchronous copy program 222, and an IO control program 223 controllingan input/output request from the host computer based on an instructionfrom the copy management program are executed on the processor 144.These programs are stored in the control memory 145.

The copy management program 221 manages an asynchronous remote copyprocess executed by each of the storage systems. The detail thereof willbe described later. During the asynchronous remote copy process,communication is performed at all times between the copy managementprograms 221 of the storage controllers 140 to exchange necessarymanagement information. The IO control program 223 executes aninput/output process to the storage device 121 based on an instructionfrom each of the host computers.

The storage controller 140 executes an input/output process to thestorage device 121 based on an instruction from each of the hostcomputers in addition to the processes of the copy management program221, the asynchronous copy program 222, and the IO control program 223.

One or more logical storage areas (volumes) are created in or relatedwith the storage device 121. In each of the host computers 110, theapplication program 211 used by the user and the program (hereinafter,called a “storage system manager”) 212 as a storage system controlinterface are executed on the processor 111 owned by the host computer110. The copy management program and the storage system manager 212 sendor receive information to/from each other. The management terminal 130executes a management program 231. The management terminal 130 executesthe management program 231 to manage the components of the computersystem of this embodiment, specifically, the host computers 110 and thestorage systems 120. The program 231 is stored in the main memory of themanagement terminal 130.

The programs described here are installed on a recording medium owned byeach of the devices using a portable medium such as a compact disc or anoptical magnetic disc or via the network 170.

(II) Data Structure Used in the Computer System

A data structure used in the computer system of this embodiment will bedescribed using FIGS. 3 to 6.

FIG. 3 is a diagram showing volume management information.

FIG. 4 is a diagram showing consistency group management information.

FIG. 5 is a diagram showing asynchronous remote copy data information.

FIG. 6 is a diagram showing configuration information on control of theamount of delay of asynchronous remote copy.

The volume management information will be described using FIG. 3.

Volume management information 300 is information managing a remote copypair and is information owned by each remote copy pair volume, which isstored in the control memory 145 of each of the storage systems 120.

The volume management information 300 includes a volume ID 310 foridentifying a volume in the storage system, and pair volume information320 as information on a data volume as a remote copy pair.

The pair volume information 320 includes a storage system ID 321, avolume ID 322 identifying a pair volume, a pair state 323 showing aduplication state, a differential bit map valid flag 324, and adifferential bit map 325.

The storage system ID 321 is an identifier of the storage system inwhich a pair volume exists, and the volume ID 322 is a volume identifierin the storage system. The storage system ID 321 is combined with thevolume ID 322 to uniquely decide a pair volume.

The pair state 323 refers to any one of the states of “PAIR” in which adata volume is in a state of duplication (in a state that there is dataconsistency in the volume), “COPY” in which differential copy is beingperformed, and “SUSPEND” in a state of suspend in which a copy processis stopped by blockage of a volume or path. The differential bit mapvalid flag 324 indicates whether a value of the differential bit map isvalid. The differential bit map 325 is information indicating an area inwhich data of PVOL and SVOL are different. A volume area is divided intoa plurality of areas, and when the data volume is updated during theSUSPEND, the bit indicating the updated area is allowed to be ON. Afterthe SUSPEND, only the area in which the bit is ON is copied(differential copied) based on the bit map by carrying out OR of thedifferential bit map 325 of each of the PVOL and SVOL to return the pairto the duplication state. The differential copy can reduce the amount ofcopy transfer. In the differential copy, the bit is allowed to be OFF inthe copied area, and when all bits are OFF, the differential copy iscompleted. All bits of the differential bit map are allowed to be ON atpair create to perform the differential copy (initial copy) to copy allareas of the PVOL to the SVOL.

Consistency group management information will be described using FIG. 4.

The consistency group management information is information for managinga consistency group and is stored in the control memory 145 of each ofthe storage systems 120.

The consistency group management information includes a consistencygroup ID 410, the latest sequence number 420, a formalized sequencenumber 430, a pair state 440, volume information 450, and delayinformation 460.

Here, the consistency group refers to a plurality of remote copy pairsrelated with each other. A write request from the host computer to theprimary volume in the consistency group maintains the write requestorder in the consistency group to be copied to the secondary volume asthe remote copy pair of the primary volume. To maintain the write order,a serial number (sequence number 510) is given to each remote copy writedata.

The secondary storage system can reflect the remote copy write datawhose sequence numbers are complete and cannot reflect the remote copywrite data with any lacked lower sequence number. A process of decidingthat the remote copy write data can be reflected in the secondarystorage system is called formalization.

The consistency group ID 410 is an identifier uniquely deciding theconsistency group.

The latest sequence number 420 is a number given latest of the sequencenumbers given to the asynchronous remote copy write data of theconsistency group.

The formalized sequence number 430 is the sequence number of the remotecopy write data which has been formalized in the secondary storagesystem.

The pair state 440 refers to any one of the states of “PAIR” in whichall pairs in the consistency group is in a state of duplication, “COPY”in which one or more pairs in the consistency group are beingdifferential copied, “SUSPEND” in which all pairs in the consistencygroup are in a state of suspend (in a state that there is dataconsistency in the consistency group), and “SUSPEND-E” in which somepairs in the consistency group are in a state of suspend (in a statethat there is no data consistency in the consistency group).

The volume information 450 includes the volume management information300 of each of the pairs included in the consistency group.

The delay information 460 is information expressing the difference inwrite update of remote copy between the primary storage system and thesecondary storage system.

The primary storage system remote copies write data to the secondarystorage system asynchronous to a write request from the host computer.Therefore, there can be some write data which has been written into thepair volume of the primary storage system, and has not been remotecopied and reflected in the secondary storage system. The delay ofreflection in the secondary storage system is called delay ofasynchronous remote copy.

The information on the amount of delay 460 includes delay timedifference 461, the number of delay updates (writes) 462, and the amountof delay update (write) data 463.

The delay time difference 461 indicates the difference between time atwhich the remote copy write data reflected in the secondary storagesystem is updated by the primary storage system and the current time.

The number of delay updates (writes) 462 indicates the number of writerequests from the host computer received by the primary storage systemafter the point of time at which the remote copy write data reflected bythe secondary storage system is updated by the primary storage system.

The amount of delay update (write) data 463 indicates the sum of theamount of write data of the write request from the host computerreceived by the primary storage system after the point of time at whichthe remote copy write data reflected by the secondary storage system isupdated by the primary storage system.

The asynchronous remote copy data information will be described usingFIG. 5.

The asynchronous remote copy data information is data transferred fromthe primary storage system to the secondary storage system.

The asynchronous remote copy data information includes a sequence number510, data 520, an address 530, and time stamp 540.

The sequence number 510 is a serial number given to maintain the writeorder in the consistency group, as described above.

The data 520 is a copy of data written into the primary volume. Thesecondary volume is write updated as in the primary volume.

The address 530 indicates a location for writing write data in thesecondary storage system.

The time stamp 540 indicates time at which the primary storage systemreceives a write request.

The configuration information on control of the amount of delay ofasynchronous remote copy will be described using FIG. 6.

The configuration information on control of the amount of delay isconfiguration information for operation so as to reduce the amount ofdelay when the amount of delay of asynchronous remote copy is increased,in order to prevent the amount of data loss of the primary site indisaster from being increased. The configuration information on controlof the amount of delay is owned by each of consistency groups and isstored in the control memory 145 of each of the storage systems 120.

The configuration information on control of the amount of delay includesa valid flag of control of the amount of delay 610, configurationinformation on time difference 630, configuration information on thenumber of updates (writes) 640, and configuration information on theamount of update (write) data 650. The valid flag of control of theamount of delay indicates whether a process of reducing the amount ofdelay is operated to the consistency group when the amount of delay ofasynchronous remote copy is increased. The configuration information ontime difference 630 includes a valid flag 631, a control start thresholdvalue 632, a control stop threshold value 633, and operation in control634. The valid flag 631 indicates whether control is performed so as toreduce the amount of delay (hereinafter, called a process of reducingthe amount of delay) when the delay time difference is increased. Thecontrol start condition 632 is a condition starting the process ofreducing the amount of delay. Specifically, it is the threshold value ofthe delay time difference starting control. The control stop condition633 is a condition stopping the process of reducing the amount of delaywhich is being executed. Specifically, it is the threshold value of thedelay time difference when stopping the process, which is a valuesmaller than that of the above start condition. The operation in control634 indicates how the process of reducing the amount of delay isperformed. As a specific process of reducing the amount of delay, forexample, a response the storage system at the primary site sends to thehost computer may be delayed to a write request from the host computerto the primary volume of the consistency group. The response is delayedto limit input of the write request from the host computer to thestorage system at the primary site. Since the asynchronous remote copyis continued, the amount of delay is gradually reduced. As anotherprocess of reducing the amount of delay, the priority of the remote copyprocess of the consistency group may be increased. Increase in thepriority of the remote copy frequently performs transfer, and the amountof delay is gradually reduced. As a further process of reducing theamount of delay, the number of transfer lines of the remote copy may beincreased. Increase in the number of paths enhances the transfer abilityof the remote copy, and the amount of delay is gradually reduced. Theoperation in reduction 634 includes one or more operations of theprocesses of reducing the amount of delay.

The configuration information on the number of updates 640 and theconfiguration information on the amount of update data 650 also includevalid flags 641, 651, control start conditions 642, 652, control stopconditions 643, 653, and operation in control 644, 654, respectively.

(III) Processes of the Computer System

Processes of the computer system according to the first embodiment ofthe present invention will be described using FIGS. 7 and 12.

(III-1) Process of Creating a Remote Copy Pair

A process of creating a remote copy pair according to the firstembodiment of the present invention will be described using FIG. 7.

FIG. 7 is a flowchart showing the process of creating a remote copy pairof the computer system according to the first embodiment.

The user inputs a pair create command to the storage system using GUI(Graphical User Interface) owned by the host computer 110, themanagement terminal 130 or the maintenance terminal 122 (S701). The paircreate command is a command relating a primary volume (hereinafter,called “PVOL”) 825 owned by the primary storage system 120A as a sourceof remote copy with a secondary volume (hereinafter, called “SVOL”) 826owned by the secondary storage system 120B as a target of the remotecopy stored in the PVOL. This process may be performed to a plurality ofvolumes. The user inputs a command relating, as a consistency group, aplurality of pairs of the remote copy related with each other in S701(S702). A plurality of consistency groups may be created.

The user inputs the configuration information on control of the amountof delay to the consistency group created in S702 of the input of thepair create command (S703). The information itself described in FIG. 6may be directly inputted. For example, the user inputs the upper limitvalue of the amount of delay, and the storage system may convert it tothe control start threshold values 632, 642, 652 and the control stopthreshold values 633, 643, 653 so that the amount of delay is within theupper limit value.

After creating the consistency group, the configuration information oncontrol of the amount of delay may be inputted after remote copy isstarted. A once inputted value may be re-inputted to change it.

After the consistency group has been created, remote copy is executed(S704). The process of reducing the amount of delay is performedaccording to the state during execution of the remote copy. The detailof the decision process of the process of reducing the amount of delaywill be described later.

Data stored in the PVOL 825 before starting the remote copy are nottransferred to the secondary storage system after the remote copy isstarted. Separately, the data (hereinafter, called “initial data”) mustbe copied from the PVOL 825 to the SVOL 826. In this embodiment, aninitial copy process of transferring the initial data from the PVOL 825to the SVOL 826 is executed (S705). The initial data from the volumehead area to the volume last area of the PVOL 825 are transferred.

(III-2) Overview of a Process of Controlling the Amount of Delay

A process of controlling the amount of delay of asynchronous remote copywill be described using FIG. 8.

FIG. 8 is a diagram showing the operation of the process of controllingthe amount of delay of asynchronous remote copy according to the firstembodiment of the present invention.

The storage systems 120A and 120B respectively execute the copymanagement program 221 to control the remote copy process. The primarystorage system 120A updates the amount of delay of asynchronous remotecopy (S802) according to a write process (S801) from the primary hostcomputer 110A to the PVOL 825. The detail of the process of updating theamount of delay (S802) will be described later. The primary storagesystem 120A returns a write completion response to the primary hostcomputer 110A.

The primary storage system 120A executes the asynchronous copy program222 to transfer a copy of data written into the PVOL 825 to thesecondary storage system 120B (S803). At this time, the primary storagesystem 120A may give a write request to the secondary storage system120B to realize data transfer, or the secondary storage system 120B maygive a read request to the primary storage system 120A to realize datatransfer.

The secondary storage system 120B executes the asynchronous copy program222 to write into the SVOL 826 the transferred remote copy write datawhose sequence numbers are complete (S804). Here, without directlywriting the transferred remote copy write data into the SVOL 826, thismay be realized by a method of writing the transferred remote copy writedata into another volume to reflect the data to the SVOL 826.

The copy management program 221 of the primary storage system 120A andthe copy management program 221 of the secondary storage system 120Bexchange information on the copy state of the remote copy (S805).Specifically, the information exchanged is the latest sequence number ofthe remote copy write data which has been formalized by the secondarystorage system 120B.

The copy management program 221 of the primary storage system 120Aupdates the amount of delay of asynchronous remote copy from theinformation on the copy state of the remote copy received from thesecondary storage system 120B. When the amount of delay of asynchronousremote copy meets the configuration condition, the process of reducingthe amount of delay is started. The detail of the process of updatingthe amount of delay and the decision process of the process of reducingthe amount of delay will be described later.

As the process of reducing the amount of delay, the copy managementprogram of the primary storage system 120A gives an instruction to theIO control program 223 to delay a write request response from theprimary host computer 110A (S806), and gives an instruction to theasynchronous copy program to increase the priority of remote copy(S807), and the copy management program 221 of the primary storagesystem 120A gives an instruction via the copy management program 221 ofthe secondary storage system 120B to delay a response to an input/outputrequest from the secondary host computer 110B (S808), thereby reducingthe load of the secondary storage system, increasing the priority of theprocess of formalizing the remote copy write data by the asynchronouscopy program (S809), and increasing the number of transfer lines of theremote copy.

(III-3) Process of Updating the Amount of Delay of Asynchronous RemoteCopy

A process of updating the amount of delay of asynchronous remote copywill be described using FIGS. 9 and 10.

FIG. 9 is a flowchart showing the process of updating the amount ofdelay of asynchronous remote copy at a write request.

When the primary storage system 120A receives from the primary hostcomputer 110A a write request in the PVOL 825 as a remote copy pair(S901), the primary storage system 120A creates remote copy data (S902).To the sequence number of the remote copy data, there is given a valueobtained by adding 1 to the latest sequence number 420 of theconsistency group including the PVOL 825. Time at which the writerequest is received is given as time stamp.

Adding 1 to the number of delay updates of the consistency groupincluding the PVOL 825 (S903), the data size of the write request isadded to the amount of delay update data 363 (S904). The differencebetween the time stamp given to the remote copy data of the formalizedsequence number 430 owned by the primary storage system 120A and thecurrent time is the delay time difference 461 (S905).

FIG. 10 is a flowchart showing the process of updating the amount ofdelay of asynchronous remote copy when the copy management programs 221of the storage systems 120 exchange the copy state of remote copy.

The copy management program 221 of the primary storage system 120Aobtains, from the copy management program 221 of the secondary storagesystem 120B, the latest number of the sequence numbers of the remotecopy data which have been formalized in the secondary storage system120B (S1001).

The past formalized sequence number 430 stored in the primary storagesystem 120A is N, and the formalized sequence number obtained from thesecondary storage system 120B is M (S1002).

The sum of the amount of data of the remote copy data given the sequencenumbers from M+1 to N is subtracted from the amount of delay update data463 owned by the primary storage system 120A (S1003, S1004, S1005, andS1006). The formalized sequence number 430 owned by the primary storagesystem 120A is changed to M (S1007).

The difference between the latest sequence number 420 owned by theprimary storage system 120A and the changed formalized sequence number430 is the number of delay updates 462 (S1008).

The difference between the time stamp given to the remote copy data ofthe changed formalized sequence number 430 owned by the primary storagesystem 120A and the current time is the delay time difference 461(S1009).

(III-4) Process of Deciding Control of the Amount of Delay ofAsynchronous Remote Copy

A process of deciding control of the amount of delay of asynchronousremote copy will be described using FIGS. 11 and 12.

The start decision process of the process of reducing the amount ofdelay of asynchronous remote copy will be described using FIG. 11. FIG.11 is a flowchart showing the start decision process of the process ofreducing the amount of delay.

The primary storage system 120A performs the process of deciding controlof the amount of delay of asynchronous remote copy independently of thewrite request from the primary host computer 110A and the copy stateinformation exchange of remote copy with the secondary storage system120B. The process of deciding control of the amount of delay may beperformed in synchronization with the write request and the copy stateinformation exchange of remote copy.

The copy management program 221 of the primary storage system 120Achecks the valid flag of control of the amount of delay 610 to decidewhether it is targeted for control of the amount of delay (S1101). Whenit is not targeted for control of the amount of delay, the remote copyis continued (S1106). When it is targeted for control of the amount ofdelay, a flag 470 in which the amount of delay is being controlled ischecked to decide whether the process of reducing the amount of delay isbeing currently performed (S1102). When the process of reducing theamount of delay is being performed, the routine is moved to the processin which the amount of delay is being reduced (S1108).

When the process of reducing the amount of delay is not performed,whether control of the amount of delay by the delay time difference isvalid is decided by the valid flag 631. Whether it is valid and thecurrent delay time difference 461 meets the control start condition 632is decided (S1103). When it meets the condition, the process of reducingthe amount of delay is started based on the operation in control of theamount of delay 634 (S1107).

When the process of reducing the amount of delay is not started by thedelay time difference, the start decision of the process of reducing theamount of delay for the number of delay updates and the amount of delayupdate data is performed in the same manner (S1104 and S1105). When theymeet the condition, the process of reducing the amount of delay isstarted based on the operation in control of the amount of delay 644,654 (S1107).

When not meeting any of the start conditions of the process of reducingthe amount of delay for the delay time difference, the number of delayupdates and the amount of delay update data, the remote copy iscontinued (S1106).

The stop decision process of the process of reducing the amount of delayof asynchronous remote copy will be described using FIG. 12.

FIG. 12 is a flowchart showing the stop decision process of the processof reducing the amount of delay.

When the process of reducing the amount of delay is being performed, thecopy management program 221 of the primary storage system 120A decidesby the valid flag 631 whether the decision of control of the amount ofdelay by the delay time difference is valid. Whether the decision isinvalid or valid and the current delay time difference 461 meets thecontrol stop condition 632 is decided (S1201). When it does not meet thecondition, the process of reducing the amount of delay is continuedbased on the operation in control of the amount of delay 634 (S1205).

When meeting the condition by the delay time difference, the number ofdelay updates is decided in the same manner (S1202). The amount of delayupdate data is alike (S1203).

When meeting all stop conditions of the process of reducing the amountof delay for the delay time difference, the number of delay updates andthe amount of delay update data, the flag 470 in which the process ofreducing the amount of delay is being performed is allowed to be OFF tostop the process of reducing the amount of delay of remote copy (S1204).

Embodiment 2

A second embodiment according to the present invention will be describedusing FIG. 13.

FIG. 13 is a diagram showing the operation of a process of controllingthe amount of delay of asynchronous remote copy according to the secondembodiment of the present invention.

A computer system of the second embodiment is different from the firstembodiment in that as shown in FIG. 13, a copy management program 1321is included in the host computer 110, not in the storage system 120, andthat an IO control program 1323 is also included in the host computer110. Each of the host computers has a communication line coupled to eachother. The copy management program 1321 performs communication with theprimary host computer 110A and the secondary host computer 110B. Thecopy management program 1321 and the IO control program of the primaryhost computers and the secondary host computers are communicated witheach other.

In the primary site 100A, to update of data of the PVOL (S801), remotecopy data is created by the primary storage system. The remote copy datainformation (the sequence number 510, the data 520, the address 530, andthe time stamp 540) is transferred to the primary host computer 110A(S1302).

The primary host computer 110A updates the delay information based onthe obtained remote copy data information. A specific process ofupdating delay information is similar to that of the first embodiment.

The asynchronous remote copy process (S803) from the primary storagesystem 120A to the secondary storage system 120B and the process ofwriting transferred remote copy write data in the secondary storagesystem 120B (S804) are similar to those of the first embodiment.

The asynchronous transfer program 222 of the primary storage system 120Btransfers the state of the formalizing process (the formalized sequencenumber) to the secondary host computer 110B (S1310).

The copy management program 1321 of the primary host computer 110A andthe copy management program 221 of the secondary host computer 110Bexchange information on the copy state of remote copy (S1305).Specifically, the information exchanged is the latest sequence number ofthe remote copy write data which has been formalized by the secondarystorage system 120B. The copy management program 221 of the primary hostcomputer 110A updates the amount of delay of asynchronous remote copyfrom the information on the copy state of remote copy received from thesecondary host computer 110B. When the amount of delay of asynchronousremote copy meets the configuration conditions, the process of reducingthe amount of delay is started. The process of updating the amount ofdelay and the decision process of the process of reducing the amount ofdelay are similar to those of the first embodiment.

As the process of reducing the amount of delay, the copy managementprogram of the primary host computer 110A gives an instruction to theprimary IO control program 223 to delay a write request response fromthe primary host computer 110A (S1306), and gives an instruction to theasynchronous copy program to increase the priority of remote copy(S1307), and the copy management program 1321 of the primary hostcomputer 110A gives an instruction via the copy management program 221of the secondary host computer 110B to the secondary storage system todelay a response to an input/output request from the secondary hostcomputer 110B (S1308), thereby reducing the load of the secondarystorage system, increasing the priority of the process of formalizingthe remote copy write data by the asynchronous copy program (S1309), andincreasing the number of transfer lines of the remote copy. This issimilar to the first embodiment. As another process of reducing theamount of delay, the copy management program of the primary hostcomputer 110A gives an instruction to the IO control program 1323 ofeach of the primary host computers 110A to reduce write requests to theprimary storage system (S1311), and gives an instruction to the IOcontrol program 1323 of each of the secondary host computers 110B viathe copy management program of the secondary host computer 110B toreduce input/output requests to the secondary storage system, reducingthe load of the secondary storage system (S1312).

(The features of the computer system and the asynchronous remote copymethod of the computer system of the present invention according to theabove embodiments)

The computer system and the asynchronous remote copy method of thecomputer system of the present invention, which are described above,asynchronous remote copy is performed by the storage system, the amountof delay of the asynchronous remote copy is managed by the storagesystem or the host computer, and the process of reducing the amount ofdelay is performed by the storage system and the host computer when theamount of delay of the asynchronous remote copy is increased. When theamount of delay of the asynchronous remote copy exceeds theconfiguration value, the operation reducing the amount of delay isstarted so that the amount of data of the primary site lost in disastercan be within a certain configuration value.

1. A remote copy system comprising: a primary site having a firststorage system coupled to a host computer; and a secondary site having asecond storage system, wherein said first storage system is coupled tosaid second storage system via a communication line, wherein said firststorage system receives a write request from said host computer,asynchronously transfers write data transferred according to said writerequest to said second storage system via said communication line, andwrites said write data into a first storage area owned by said firststorage system, wherein said second storage system writes the write datatransferred from said first storage system into a second storage areaowned by said second storage system, wherein said first storage systemrecognizes a size of differential data which is data written into saidfirst storage area but not written into said second storage area,decides whether to start a process to reduce said size based on whethersaid size is larger than a threshold, and stops said process based onsaid size having been reduced, after said process is started, andwherein said process includes limiting input of write requests from saidhost computer to said first storage system.
 2. The remote copy systemaccording to claim 1, wherein said first storage system recognizes anamount of delay of data write between said first storage system and saidsecond storage system based on obtained information, wherein said amountof delay is a difference in data write times between a data write atsaid first storage system and a data write at said second storagesystem, and wherein a process of reducing the amount of delay isexecuted when said amount of delay exceeds a predetermined thresholdvalue.
 3. The remote copy system according to claim 2, wherein saidoperation reducing the amount of delay is an operation in which saidfirst storage system delays sending of a write completion report sent tosaid host computer.
 4. The remote copy system according to claim 2,wherein said operation reducing the amount of delay is an operationincreasing the priority of a data transfer process from said firststorage system to said second storage system.
 5. The remote copy systemaccording to claim 2, wherein said operation reducing the amount ofdelay is an operation increasing the number of paths used for the datatransfer process from said first storage system to said second storagesystem.
 6. A remote copy system comprising: a primary site having afirst storage system coupled to a host computer; and a secondary sitehaving a second storage system, wherein said first storage system iscoupled to said second storage system via a communication line, whereinsaid first storage system receives a write request from said hostcomputer, asynchronously transfers write data transferred according tosaid write request to said second storage system via said communicationline, and writes said write data into a first storage area owned by saidfirst storage system, wherein said second storage system writes thewrite data transferred from said first storage system into a secondstorage area owned by said second storage system, wherein said firststorage system recognizes a size of differential data which is datawritten into said first storage area but not written into said secondstorage area resulting from a difference in the number of data writesbetween data writes at said first storage system and data writes at saidsecond storage system, decides whether to start a process to reduce saidsize based on whether said size is larger than a threshold, and stopssaid process based on said size having been reduced, after said processis started, and wherein said process includes limiting input of writerequests from said host computer to said first storage system.
 7. Theremote copy system according to claim 6, wherein said first storagesystem recognizes an amount of delay of data write between said firststorage system and said second storage system based on obtainedinformation, wherein said amount of delay is said difference in thenumber of data writes between data writes at said first storage systemand data writes at said second storage system, and wherein a process ofreducing the amount of delay is executed when said amount of delayexceeds a predetermined threshold value.
 8. The remote copy systemaccording to claim 7, wherein said operation reducing the amount ofdelay is an operation in which said first storage system delays sendingof a write completion report sent to said host computer.
 9. The remotecopy system according to claim 7, wherein said operation reducing theamount of delay is an operation increasing the priority of a datatransfer process from said first storage system to said second storagesystem.
 10. The remote copy system according to claim 7, wherein saidoperation reducing the amount of delay is an operation increasing thenumber of paths used for the data transfer process from said firststorage system to said second storage system.
 11. A remote copy systemcomprising: a primary site having a first storage system coupled to ahost computer; and a secondary site having a second storage system,wherein said first storage system is coupled to said second storagesystem via a communication line, wherein said first storage systemreceives a write request from said host computer, asynchronouslytransfers write data transferred according to said write request to saidsecond storage system via said communication line, and writes said writedata into a first storage area owned by said first storage system,wherein said second storage system writes the write data transferredfrom said first storage system into a second storage area owned by saidsecond storage system, wherein said first storage system recognizes asize of differential data which is data written into said first storagearea but not written into said second storage area resulting from adifference in the number of data writes between data writes at saidfirst storage system and data writes at said second storage system,decides whether to start a process to reduce said size based on whethersaid size is larger than a threshold, and stops said process based onsaid size having been reduced, after said process is started, whereinsaid size being larger than the threshold indicates that an amount ofdelay resulting from a difference in the number of data writes betweendata writes at said first storage system and data writes at said secondstorage system exceeds a predetermined threshold value, and wherein saidprocess includes limiting input of write requests from said hostcomputer to said first storage system.
 12. The remote copy systemaccording to claim 11, wherein said first storage system recognizes anamount of delay of data write between a data write at said first storagesystem and a data write at said second storage system based on obtainedinformation, wherein a process of reducing the amount of delay isexecuted when said amount of delay exceeds a predetermined thresholdvalue, and wherein said operation reducing the amount of delay is anoperation in which said first storage system delays sending of a writecompletion report sent to said host computer.
 13. The remote copy systemaccording to claim 12, wherein said operation reducing the amount ofdelay is an operation increasing the priority of a data transfer processfrom said first storage system to said second storage system.
 14. Theremote copy system according to claim 12, wherein said operationreducing the amount of delay is an operation increasing the number ofpaths used for the data transfer process from said first storage systemto said second storage system.
 15. The remote copy system according toclaim 12, wherein said amount of delay is a difference in an amount ofdata writes between said first storage system and said second storagesystem.
 16. The remote copy system according to claim 2, wherein saiddifference in data write times is a difference between a time at which adata write is performed in the first storage system to store write datain the first storage system and a current time of a data write performedin the second storage system to update remote copy data stored in thesecond storage system based on the write data from the first storagesystem.
 17. The remote copy system according to claim 7, wherein saiddifference in the number of data writes is a difference in the number ofdata writes performed in the first storage system to store write data inthe first storage system and the number of data writes performed at thesecond storage to update remote copy data stored in the second storagesystem based on the write data during a period of time.
 18. The remotecopy system according to claim 15, wherein said difference in the amountof data writes is a sum of an amount of write data of data writesperformed at the first storage system based on write requests from thehost computer after a point in time at which remote copy data stored bythe second storage system is updated by the first storage system. 19.The remote copy system according to claim 12, wherein said operationreducing the amount of delay is stopped when meeting a stop condition bythe process of reducing the amount of delay.